The present invention relates to a library apparatus that reads and writes data from and to a magnetic cartridge tape used as the recording medium, and particularly to a library apparatus adapted to correct the alignment of a leader block attached to the leading end of a recording tape, so that the tape can be pulled out of its cartridge by the leader block.
Some computer systems include at least one library apparatus which stores a plurality of magnetic tape cartridges in the racks of its cell units. In this type of library apparatus, after the desired cartridge is ejected from a rack in response to a command from the computer and is set in a magnetic tape apparatus, backup data are written to or read from the cartridge.
FIG. 21 is a schematic of the structure of a conventional library apparatus. In this drawing, auto cartridge loader (ACL) 10 includes a cell unit (not shown in FIG. 21) for storing a plurality of cartridges 300 shown in FIGS. 22 and 23, and an accessor mechanism (ACC) (not shown in FIG. 21) that automatically transfers a cartridge 300 to the cell unit or a magnetic tape unit (MTU) 20, to be described later, in response to commands from the computer (not shown).
The cell unit described above is constructed from a plurality of racks called cells. The cartridges 300 are stored in these cells. The ACC ejects a cartridge 300 from the desired cell in the cell unit in response to commands from the computer and automatically transfers it to the MTU 20. In addition, the ACC ejects a cartridge 300 from the MTU 20 and automatically transfers it to a cell in the cell unit.
FIG. 22 is a perspective view showing the structure of the cartridge 300 in an upright state. FIG. 23 is a perspective view showing the structure when the cartridge 300 has been turned over. A cartridge case 301 of the cartridge 300 has a generally box shape and accommodates a tape 302, which is the magnetic recording medium, wound around a tape reel 304. Data is written to or read from this tape 302 by the MTU 20.
A cartridge top 301c of the cartridge case 301 is formed from a transparent resin. Thus, the tape 302 wound around the tape reel 304 can be checked from the outside through the cartridge top 301c. A leader block latch 301b is an opening formed on the left side of a side surface 301a and functions as a leader port to pull out the tape 302 from the cartridge 300 and to latch or hold a leader block 303 to the cartridge case 301.
The leader block 303 is attached to a tip 302a of the tape 302 and is the member that engages a threader pin 234 (shown in FIG. 24A) when the tape 302 is pulled out of the cartridge 300 and when the pulled out tape 302 is stored back in the cartridge 300. The tape tip 302a is attached and fixed to a tape tip mount 303a. The threader pin latch 303b is formed to have a nearly hook-shaped cross-section to engage the threader pin 234.
In the above structure, in response to commands from the computer, the ACC of the ACL 10 ejects a cartridge 300 from the desired cell in the cell unit and automatically transfers it to a transfer position on the MTU 20. The threader pin 234 is positioned at the initial position in the MTU 20 as shown in FIG. 25A. Then the MTU 20 loads the cartridge 300 from the transfer position to a read/write position, where the threader pin latch 303b of the leader block 303 engages the threader pin 234 as shown in FIG. 25A. Next, as shown in FIG. 25B, under the control of the MTU 20, the tape reel 304 is rotated forward by a motor (not shown), and the tape 302 is pulled out of the cartridge 300 by the motion of the threader pin 234 in the X+ direction. Then the MTU 20 reads from or writes to the tape 302.
When the reading or the writing process on the tape 302 is finished, the tape reel 304 is rotated backwards by a motor (not shown), and the tape 302 is wound back inside the cartridge 300 by the motion of the threader pin 234 in the opposite direction to the X+ direction.
Next, the MTU 20 unloads the cartridge 300 from the read/write position to the transfer position. The ACC in the ACL 10 ejects the cartridge 300 from the MTU 20 and automatically transfers it to the desired cell of the cell unit in the ACL 10. Thus, the cartridge 300 is stored in a cell.
At times, the leader block 303 separates from the tape 302 in a conventional library apparatus because of pressure applied from the outside or deterioration over time. Usually, the leader block 303 can be reattached to the tape 302 by using a special tool. Often, however, the leader block 303 may be attached improperly at an incline with respect to the tape 302 as shown in FIG. 24A.
Consequently, the leader block 303 could slip and separate from the threader pin 234 while the tape 302 is being pulled out of the cartridge 300 by the threader pin 234. Typically, when this occurs, after the tape 302 is temporarily stored back in the cartridge 300 and the cartridge is unloaded from the MTU 20, then the cartridge 300 is reloaded and a retry of the read or write process is performed. That is, when a leader block slip occurs, the tape reel 304 is rotated to store the tape 302 back in the cartridge 300. As shown in FIG. 24C, however, the leader block 303 does not fully latch to the leader block latch 301b (best shown in FIG. 22) because the leader block is mounted at an incline with respect to the tape 302. Next, the threader pin 234 moves towards the leader block 303 in the Xxe2x88x92 direction. As shown in FIG. 24D, the threader pin 234 does not properly engage the leader block 303 because the leader block has not engaged the leader block latch 301b properly. As a result, the threader pin 234 and its supporting parts could become damaged when the threader pin collides with the leader block 303, requiring not only the threader pin 234, but other related parts to be replaced, which increases maintenance costs.
In the properly attached state, if a retry is performed with the leader block 303 attached to the tape 302, the leader block will be fully latched to the leader block latch 301b. Therefore, the threader pin 234 will not collide with the leader block 303.
Another problem associated with a conventional library apparatus is that the driving force of the motor (not shown) that rotates the tape reel 304 backwards becomes weaker over time due to deterioration. As a result, the leader block 303 incompletely latches to the leader block latch 301b when the tape 302 is wound in the cartridge 300. In this case, since the leader block 303 of the cartridge 300 is stored in a cell in an incompletely latched state, the leader block 303 must be pushed into the leader block latch 301b, which is a serious problem in maintenance management.
Accordingly, one object of this invention is to provide improved library apparatus which prevents a threader pin from colliding with and damaging the leader block of a tape cartridge.
Another object of this invention is to provide improved library apparatus having a magnetic tape unit which holds a cartridge in a position where the threader pin is prevented from colliding with and damaging the leader block of the cartridge.
Yet another object of this invention is to provide improved library apparatus having a pressing device which is adapted to push the leader block into a latch provided on the cartridge.
In keeping with one aspect of this invention, a library apparatus is adapted to write to and read from a plurality of cartridges each housing a tape wound around a reel. The tape has a leader block attached to a tip thereof for pulling the tape out of its cartridge and adapted to be seated in a leader block latch provided on the cartridge. The apparatus includes a cell unit having a plurality of cells for storing the tape cartridges, a threader unit for writing data to and/or reading data from a selected cartridge. The threader unit has a pin for engaging the leader block and pulling the tape out of the cartridge for writing and/or reading data on the tape. A loading unit is connected to the threader unit for holding the cartridge in a first position where the pin is prevented from engaging the leader block of the cartridge, and a second position where the pin is allowed to engage the leader block. An accessor transfers the cartridge between the cell unit and the first position of the loading unit. Also included in the apparatus is a feature for determining whether the pin has properly engaged the leader block of the cartridge in the second position, and a pressing device for pushing the leader block into proper alignment when it is determined that the pin has not properly engaged the leader block.